The long-term outcome after surgical reimplantation of a unilateral congenitally anomalous pulmonary artery (UCAPA) origin is inadequately described. We performed a single-center retrospective review of patients with pulmonary artery (PA) sling or anomalous origin of 1 PA from the ascending aorta who underwent surgical repair from 1980 to 2006. Baseline data were available for 20 patients with PA sling and 29 patients with anomalous origin of 1 PA from the ascending aorta. Follow-up data for 38 patients, representing 190 cumulative patient-years, were available. Of 28 (74%) patients who developed pulmonary artery stenosis (PAS), 17 (45%) patients underwent a first intervention for PAS, and 9 (24%) patients underwent a second intervention. Median time from surgical repair to diagnosis of PAS was 0.4 years (95% confidence interval [CI] 0, 0.9). Median time from diagnosis of PAS to first intervention was 2.7 years (95% CI 0.07, 5.4). In the 29 patients initially repaired at our center, no first intervention occurred later than 2.8 postoperative years. Median time from first to second intervention was 2 years (95% CI 0, 4.8). Percutaneous intervention for postoperative PAS resulted in acute hemodynamic and anatomic improvement with modest risk profile. On multivariate analysis, recent surgical repair (after 1993) was a risk factor for PAS (p = 0.03, hazard ratio [HR] 1.9), and operative first intervention (vs. percutaneous) was a risk factor for second intervention (p = 0.05, HR 11.2). After reimplantation of a UCAPA origin, PAS is frequent and occurs early postoperatively. Close follow-up after repair is necessary.